Forces & Motion


Forces & Motion

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  1. Forces & Motion

    Slide 1 - Forces & Motion

  2. What is a force?

    Slide 2 - What is a force?

    • A force is a push or a pull
    • A force can be described by its strength and direction
    • The units of force are the newton (N)
    • Like velocity, we always specify a direction for a force.
    • Ex. 28 N to the right or 14 N down
  3. Net Forces

    Slide 3 - Net Forces

    • A net force is the combination of all the forces acting on an object.
    • A non-zero net force will cause an object to move
  4. Example

    Slide 4 - Example

    • Two people are pushing on opposite sides of a box.
    • The stronger person pushes with 20 N of force to the left
    • The weaker person pushes with 15 N of force to the right
    • What is the net force on the box?
    • 15 N
    • 20 N
    • 5N
    • The net force is 5 N to the left
    • The box will move to the left
  5. Force due to Friction

    Slide 5 - Force due to Friction

    • A force that two surfaces exert on each other when they are in contact and motion.
    • The friction force acts in the opposite direction than the motion of the object
    • Friction depends on the type of surfaces and how hard they surfaces are pushed together.
  6. Example of Friction

    Slide 7 - Example of Friction

    • You are pushing a box across the floor with 10N of force to the left.
    • The force due to friction is 2N.
    • What is the net force on the box?
    • 2N
    • 10N
    • 8N
    • The net force is 8N to the left.
  7. The Force due to Gravity

    Slide 8 - The Force due to Gravity

    • Gravity is a force of attraction between two objects with mass
    • The more mass an object has, the greater it’s gravitational attraction
    • The closer an object is, the greater it’s gravitational attraction
    • Gravity depends on the mass of the objects and their distance apart.
  8. Gravity on Earth

    Slide 9 - Gravity on Earth

    • On Earth, gravity always causes an object to accelerate at 9.8 m/s2
    • So when objects fall towards Earth, each second they fall 9.8m/s faster than the second before.